Giovani Lo Celso has arrived in London to complete a £55m move to Tottenham from Real Betis, Sky Sports News understands.
The Argentina international will have a medical before completing the deal, which could rise to £60m.
Betis did not include the 23-year-old in their squad for a friendly against Las Palmas on Wednesday night.
If completed, the transfer would become Spurs' second-biggest signing - behind Tanguy Ndombele, who cost them £63m from Lyon earlier this summer.
Spurs have also held talks with Sporting Lisbon over midfielder Bruno Fernandes.
They are also close to signing Ryan Sessegnon from Fulham and expect to complete a deal for the versatile left-sided player before Thursday's 5pm deadline.
Tottenham are also working to find an agreement on Paulo Dybala's personal terms, according to Sky in Italy.
Spurs agreed a £64.4m fee with Juventus for the Argentine forward on Tuesday but they have yet to reach an agreement for Dybala's image rights from company Image Star.
Follow Deadline Day on Sky Sports
It's Transfer Deadline Day for the Premier League and Championship on Thursday - and Sky Sports will be bringing you all the latest news on who your club is signing.
Start your day with Deadline Day Breakfast (6am) ahead of a special Good Morning Transfers show (9am), with Deadline Day - The Countdown (4pm) taking you to the 5pm deadline.
The Transfer Show - Deadline Day at 6pm will analyse the big moves before Deadline Day at Ten rounds up all the transfer headlines.